NMR studies on chiral intermediates in the total synthesis of (+)-biotin from D -mannose

2010 ◽  
Vol 48 (8) ◽  
pp. 651-655
Author(s):  
Wen-xue Chen ◽  
Ping Zhang ◽  
Fen-er Chen
Keyword(s):  
Total Synthesis ◽  
Nmr Studies ◽  
Chiral Intermediates

scholarly journals Camphorae: chiral intermediates for the total synthesis of steroids

1977 ◽  
Vol 99 (18) ◽  
pp. 6105-6106 ◽  
Author(s):  
Robert V. Stevens ◽  
Fred C. A. Gaeta
Keyword(s):  
Total Synthesis ◽  
Chiral Intermediates

scholarly journals Total Synthesis, Isolation, Surfactant Properties, and Biological Evaluation of Ananatosides and Related Macrodilactone-Containing Rhamnolipids

2021 ◽  
Author(s):  
Maude Cloutier ◽  
Marie-Joëlle Prévost ◽  
Serge Lavoie ◽  
Thomas Feroldi ◽  
Marianne Piochon ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Therapeutic Potential ◽  
Opportunistic Pathogen ◽  
Biological Evaluation ◽  
Specific Class ◽  
Nmr Studies ◽  
Open Chain ◽  
Surfactant Properties ◽  
Enzymatic Transformation ◽  
Human Pathogenic Bacterium

<p>Rhamnolipids are a specific class of microbial surfactants, which hold great biotechnological and therapeutic potential. However, their exploitation at the industrial level is hampered because they are mainly produced by the opportunistic pathogen <i>Pseudomonas aeruginosa</i>. The non-human pathogenic bacterium <i>Pantoea ananatis</i> is an alternative producer of rhamnolipid-like metabolites containing glucose instead of rhamnose residues. Herein, we present the isolation, structural characterization, and total synthesis of ananatoside A, a 15-membered macrodilactone-containing glucolipid, and ananatoside B, its open-chain congener, from organic extracts of <i>P. ananatis</i>. Ananatoside A was synthesized through three alternative pathways involving either an intramolecular glycosylation, a chemical macrolactonization or a direct enzymatic transformation from ananatoside B. A series of diasteroisomerically pure (1®2), (1®3), and (1®4)-macrolactonized rhamnolipids were also synthesized through intramolecular glycosylation and their anomeric configurations as well as ring conformations were solved using molecular modeling in tandem with NMR studies. We show that ananatoside B is a more potent surfactant than its macrolide counterpart. We present evidence that macrolactonization of rhamnolipids enhances their cytotoxic and hemolytic potential, pointing towards a mechanism involving the formation of pores into the lipidic cell membrane. Lastly, we demonstrate that ananatoside A and ananatoside B as well as synthetic macrolactonized rhamnolipids can be perceived by the plant immune system, and that this sensing is more pronounced for a macrolide featuring a rhamnose moiety in its native <sup>1</sup><i>C</i><sub>4</sub> conformation. Altogether our results prove that macrolactonization of glycolipids can dramatically interfere with their surfactant properties and biological activity.</p>

Camphorae: chiral intermediates for the enantiospecific total synthesis of steroids. 1

1983 ◽  
Vol 105 (26) ◽  
pp. 7713-7719 ◽  
Author(s):  
Robert V. Stevens ◽  
Fred C. A. Gaeta ◽  
David S. Lawrence
Keyword(s):  
Total Synthesis ◽  
Chiral Intermediates
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